Experimental reproduction of random pressure fields for vibroacoustic testing of plane panels

Abstract

The feasability of the experimental reproduction of random pressure fields on a plane panel and corresponding induced vibrations is studied. The random pressure fields to be reproduced, a Diffuse Acoustic Field (DAF) and a Turbulent Boundary Layer (TBL), are described using their Cross-Spectral Densities (CSD). We propose an open-loop reproduction strategy that uses the synthetic array concept, for which a small array element is moved to create a large array by post-processing. Three possible approaches are suggested to define the complex amplitudes to be imposed at the post-processing step to all the virtual reproduction sources distributed on a virtual plane, the synthetic array, facing the panel to be tested. With a setup using a single acoustic monopole, a scanning laser vibrometer and a baffled simply supported aluminum panel, we obtain experimental vibroacoustic indicators such as the Transmission Loss (TL) for DAF, subsonic and supersonic TBL excitations. The assets or weaknesses inherent to each method are discussed, in terms of their aptitudes for reproducing the target pressure field for a given array geometry. The experimental TL results are compared to simulation results obtained using a commercial software. Most of the comparisons show that the three approaches are suitable for DAF and TBL wall pressure fluctuations reproduction, and thus should open perspectives for the experimental vibroacoustic testing of fuselage panels.